From bdc4323142fe07bffe581fc1595e1e0bab0f8f8a Mon Sep 17 00:00:00 2001
From: Philipp Le <philipp-le-prviat@freenet.de>
Date: Sun, 3 May 2020 00:04:47 +0200
Subject: Adding references

---
 chapter00/preface.tex | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

(limited to 'chapter00/preface.tex')

diff --git a/chapter00/preface.tex b/chapter00/preface.tex
index 83e8ae1..4bea33e 100644
--- a/chapter00/preface.tex
+++ b/chapter00/preface.tex
@@ -2,6 +2,8 @@
 \addcontentsline{toc}{chapter}{Preface: Digital Communication -- A Future Technology}
 \chapter*{Preface: Digital Communication -- A Future Technology}
 
+\begin{refsection}
+
 The current time during the Corona lockdown shows the great significance of telecommunication. It is self-evident to have access to online media and communication platforms. The internet helps to keep in touch with our loved ones. A huge amount of entertainment relies on internet access. The internet is highly integrated in our every-day life. Furthermore, it is a growing economy. There are not only the online services like social media or online warehouses which are going to expand their business in the future. The communication technologies, which the internet is built upon, are a growing and innovative market, too. Besides consumers, the \ac{B2B} market is a huge driver of innovation. It must be expected, that more devices get interconnected. This is a challenge because physical resources are limited. Nevertheless, it is a great possibility for the communication technology to advance. The technologies, which are able to cope with the new requirementes, are digital. This where the course on \emph{Digital Communication Systems} starts. You are warmly welcomed!
 
 \addcontentsline{toc}{section}{History of Communications}
@@ -22,9 +24,21 @@ Transferring information became more important as societies advanced.
 	\item In the 18th century, semaphore lines had been built. They used visual telegraphy. Semaphores on fixed towers could display a set of symbols, which were relayed along the line.
 \end{itemize}
 
-\todo{Figure Caesar cipher}
-
-\todo{Semaphores, beacons, lighthouses}
+\begin{minipage}{0.45\linewidth}
+	\begin{figure}[H]
+		\centering
+		\includegraphics[width=\linewidth]{../chapter00/CaesarCipher.jpg}
+		\caption[Caesar cipher]{Caesar cipher. Each letter is replaced by another one which is a fixed number of letters away from the original one. \licensequote{\cite{Berberich2013}}{Hubert Berberich}{Public Domain}}
+	\end{figure}
+\end{minipage}
+\hfill
+\begin{minipage}{0.45\linewidth}
+	\begin{figure}[H]
+		\centering
+		\includegraphics[width=\linewidth]{../chapter00/OpticalTelegraph.jpg}
+		\caption[Optical telegraph]{Optical telegraph \cite{WikiSemaphore}}
+	\end{figure}
+\end{minipage}
 
 The research of electricity created the foundations for modern communication systems. Electrical telegraphy speeded up telecommunication. At the end of the 19th century, electromagnetic waves have been discovered. James Clerk Maxwell postulated them in 1865. Heinrich Hertz produced the first electromagnetic waves in 1887. The potential had soon been acknowledged by inventors, who developed first radios. The era of analogue radio communication began. The \index{vacuum tube} vacuum tube became an important component in radio electronics.
 
@@ -68,3 +82,5 @@ Understanding digital communication systems is of great importance in many engin
 	\item \textbf{Energy Sector} -- 
 \end{itemize}
 
+\printbibliography[heading=subbibliography]
+\end{refsection}
-- 
cgit v1.1

